Derivatives (Derivatives Outstanding) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014
Derivative [Line Items]
Total mark to market derivatives	$ (1.9)
Commodity
Derivative [Line Items]
Total mark to market derivatives	(1.9)
Short [Member] | Natural Gas Liquids [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	63,700,000
Total mark to market derivatives	(2.2)
Short [Member] | Natural Gas [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	1,800,000
Total mark to market derivatives	0.7
Long [Member] | Natural Gas Liquids [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	51,700,000
Total mark to market derivatives	0.3
Long [Member] | Natural Gas [Member]
Derivative [Line Items]
Derivative Nonmonetary Notional Amount	1,900,000
Total mark to market derivatives	$ (0.7)